Economical production of aluminum hydride (AlH3) or “alane” depends on an approach that combines aluminum with hydrogen in a manner that is energy efficient and practical. However, the rate of direct reaction between pure aluminum and hydrogen is very slow. A major barrier to this reaction is that little change in enthalpic energy (ΔHf=−2.37 kcal/mol AlH3) occurs in the transformation of elemental aluminum and hydrogen to aluminum hydride. The ordered nature of the crystalline aluminum metal also inhibits reaction with hydrogen. Another barrier is that the aluminum oxide (Al2O3) coating that forms on the surface of aluminum when it comes in contact with air, reduces or limits the surface area of the reactive aluminum and inhibits the reaction with hydrogen.
Methods for microcrystalline alane synthesis are inefficient for producing large quantities of alane. These methods are problematic when production of a specific alane polymorph is required, such as alpha alane (α-alane). The large amounts of solvent required as described in the patent literature for the synthesis of the alpha polymorph of alane hinder the large-scale production of this material by these routes. Material and capital equipment costs can be reduced by a dramatic reduction in solvent for this process.